Crystallization apparatus

ABSTRACT

A crystallization apparatus with a horizontal tank subdivided into a plurality of intercommunicating compartments has a plurality of walls parallel to the longitudinal axis of the tank arranged in each compartment to form therein two cells laterally adjacent the tank walls and at least one central cell. The neighboring cells in each compartment also communicate with each other, as does each cell laterally adjacent the tank walls with a like cell upstream or downstream, the ports in the dividing walls being so arranged that the product in the tank circulates therethrough in a sinuous path. Radiators are positioned in the lower part of the tank and pass through all compartments, the radiators being divided into several sections each positioned in one of the cells and forming in each cell a return passage for the product under the radiators.

United States Patent [1 1 [451 Sept. 24, 1974 FOREIGN PATENTS OR APPLICATIONS 797,552 5/1935 France 165/161 259,917 1970 U.S.S.R 165/161 Primary Examiner-Wilbur L. Bascomb, Jr. Assistant ExaminerS. J. Emery Attorney, Agent, or Firm-Kurt Kelman [5 7 ABSTRACT A crystallization apparatus with a horizontal tank subdivided into a plurality of intercommunicating compartments has a plurality of walls parallel to the longitudinal axis of the tank arranged in each compartment to form therein two cells laterally adjacent the tank walls and at least one central cell. The neighboring cells in each compartment also communicate with each other, as does each cell laterally adjacent the tank walls with a like cell upstream or downstream, the ports in the dividing walls being so arranged that the product in the tank circulates therethrough in a sinuous path. Radiators are positioned in the lower part of the tank and pass through all compartments, the radiators being divided into several sections each positioned in one of the cells and forming in each cell a return passage for the product under the radiators.

7 Claims, 3 Drawing Figures Windal CRYSTALLIZATION APPARATUS [75] Inventor: George Windal, Roubaix, France [73] Assignee: Fives Lille-Cail, Paris, France [22] Filed: Sept. 28, 1972 [21] Appl. No.: 292,858

[30] Foreign Application Priority Data Sept. 29, 1971 France 71.34999 [52] US. Cl. 23/273 R, 23/295, 159/26 R, 159/28 A, 165/160, 165/161 [51] Int. Cl BOld 9/02 [58] Field of Search 165/160, 161; 159/28 A, 159/26 R; 23/273 R, 295 R [5 6] References Cited UNITED STATES PATENTS 1,489,932 4/1924 Dickey 165/161 1,700,498 l/1929 Hughes.... 165/161 2,467,741 4/1949 Hancock 165/161 2,493,969 1/1950 James 165/161 2,830,798 4/1958 Anderson 165/161 3,424,221 H1969 Luce 23/273 R 3,609,986 10/1971 Karnofsky... 23/273 R 3,687,636 8/1972 Saurbrine. 23/273 R 3,725,127 4/1973 Retali 23/273 R I a 1 r'i 1"" '22 L I I upstream OI CRYSTALLIZATION APPARATUS The present invention relates to improvements in crystallization apparatus for crystallizing the solute of a solution by evaporating the solvent of the solution in a continuous operation. Known apparatus of this type comprises a substantially cylindrical tank having a horizontally extending longitudinal axis, a plurality of transverse walls separating the tank into a plurality of compartments, with each wall defing port means whereby the compartments are in communication, and heating means positioned in the lower part of the tank and passing through all the compartments. The heating means are constituted by vertical radiators or plates parallel to each other.

It is known that the crystals produced in such apparatus increase in regularity in direct proportion to the length of the path in which the solution and the crystallized solute pass through the apparatus and the number of the compartments, for a tank of like dimension and a like dwelling time of the product therein.

With this in mind, it has been proposed to position vertical walls parallel to the longitudinal axis of the tank in the compartments to divide each compartment into two cells communicating with each other and to form entry and exit ports for the product in each compartment of either side of the vertical dividing wall so as to force the product to circulate in a sinuous path.

It is the primary object of this invention to improve this type of crystallization apparatus so as to improve the grain size distribution of the crystals produced therein.

With this and other objects in view, a plurality of walls parallel to the longitudinal axis and transversely spaced from each other and from the tank with each other, each cell laterally adjacent the tank Walls communicates with the like cell of the downstream compartment through respective ones of the port means, and the port means is so arranged that the solution and crystallized solute circulates through the tank in a sinuous path. The heating means is divided into several sections each positioned in one of the cells and so spaced from at least one of the walls of the cells as to form in each cell a return passage for the solution and crystallized solute under the heating means.

If the heating means is constituted by vertical plates or radiators parallel to the longitudinal axis of the tank and common to several compartments, the corresponding longitudinally extending dividing walls in all of these compartments may be aligned and the heating means sections are transversely spaced from one another. Those dividing walls which are disposed in the plane of the radiator plates may, in part, be formed by these plates.

In one embodiment of the invention, the heating means is divided into two sections disposed symmetrically in respect of a longitudinal plane of symmetry of the tank, and each section is sub-divided into two subsections by a respective one of walls parallel to the longitudinal axis.

In another embodiment, the heating means is divided into a central section disposed symmetrically in respect of the plane of symmetry and two lateral sections disposed symmetrically in respect of this plane, and two walls parallel to the longitudinal axis are disposed between the central section and the lateral sections.

In either embodiment, one of the walls parallel to the longitudinal axis may be disposed in the plane of symmetry.

In either embodiment, one of the parallel to the longitudinal axis may be disposed in the plane of symmetry.

The above and other objects, advantages and features of the present invention will become more fully understood in the following detailed description of certain now preferred embodiments thereof, taken in conjunction with the accompanying schematic drawing wherein FIG. 1 is a transverse section of one embodiment of the crystallization apparatus according to this inventron;

FIG. 2 is a longitudinal section along line II-II of FIG. 1; and

FIG. 3 is a view similar to that of FIG. 1 of another embodiment.

Referring now to the drawing and first to FIGS. 1 and 2, the crystallization apparatus is shown to comprise a substantially cylindrical tank 10 having a horizontally extending longitudinal axis. A heating means is positioned in the lower part of the tank 10 and is shown to be constituted by hollow radiator plates forming heating elements, the plates extending vertically and being parallel to each other and to the longitudinal plane of symmetry of the tank. In a well known manner (not shown to simplify the illustration of the essential parts of the apparatus), steam distributing boxes are connected to the radiator plates at the respective ends of the tank to circulate heating steam therethrough.

As shown in FIG. 2, a plurality of transverse walls la, 2a, 3a, 4a, 5a, 6a, separate tank 10 into a plurality of compartments 1, 2, 3, 4, 5, 6, 7, the spacing between the transverse walls increasing from the input end of the tank to the output end thereof.

As illustrated in FIG. 1, each compartment is divided into four cells by by three walls 22 parallel to the longitudinal axis of the tank and transversely spaced from each other. Cells A and D are laterally adjacent the walls of the tank and cells B & C are positioned centrally therebetween. The neighboring cells in each compartment communicate with each other through port means in the wall 22 above or below the heating plates, the ports in the illustrated embodiment being shown below the heating plates.

As appears from the drawing, one of the walls 22 is disposed in the longitudinal plane of symmetry of the tank while the two other walls 22 are disposed symmetrically in respect of this plane laterally adjacent the two lateral sections 14 and 16 of the heating means while the central heating means section 12 is divided by the intermediate wall 22. As is shown in FIG. 1, a portion of dividing walls 22 is constituted by heating plates.

Each transverse wall defines a port 24 alternately placed to the right and to the left of the plane of symmetry adjacent the wall of tank 10, as clearly shown in FIG. 2, so that the like lateral cells A and D of neighboring compartments communicate with each other.

In operation, a concentrated solution of the solute to be crystallized is introduced into the first compartment 1 of tank 10, together with seed crystals. A controlled amount of an under-saturated solution is introduced into each compartment to maintain the concentration of the solution in all compartments at a desired level, this amount being distributed in the cells of each compartment, all in a manner well known per se and not forming part of the present invention.

In each cell, the solution and crystallized solute rise between the heating plates and descend again under the plates into' a vapor chamber above the heating means, where the vapor amasses, while passing through the passages between the heating plates and one of the cell walls. In each compartment, the charge circulates from one cell to the next by passing through the ports in the longitudinal dividing walls 22 under the heating plates, as indicated by the three arrows in FIG. I. The charge passes from compartment to compartment through the ports 24 in the transverse walls, as indicated by the curved arrows in FIG. 2. As shown by these arrows, the charge follows a sinuous path in its passage through the tank 10.

In this manner and without increasing the outer dimensions of the tank, a considerable improvement in the granular size disbribution of the produced crystals is obtained.

While the longitudinally extending walls 22 of all compartments are shown aligned in the embodiment of FIGS. 1 and 2, the walls in adjacent compartments could be transversely staggered in relation to each other, if desired.

The embodiment of FIG. 3 differs from the abovedescribed apparatus in that the heating means is divided into two sections 30 and 32 disposed symmetrically in respect of the longitudinal plane of symmetry of the tank the longitudinal walls 22' being disposed identically to walls 22. In this way, each heating means section is subdivided into two sub-sections.

If desired, the central dividing wall 22 may be omitted, thus providing two lateral cells and one central cell in each compartment. Furthermore, more than three dividing walls could be used to produce a larger number of central cells.

The crystallization apparatus herein described is particularly useful for use in sugar refineries for producing sugar crystals.

I claim:

I. A crystallization apparatus for crystallizing the solute of a solution by evaporating the solvent of the solution in a continous operation, comprising 1. a substantially cylindrical tank having a horizontally extending longitudinal axis;

2. inlet means for the solution at one end of the tank;

3. outlet means for the crystallized solute at an end of the tank opposite to the one end;

4. heating means positioned in the lower part of the tank;

5. a plurality of transverse walls separating the tank into a plurality of compartments and extending from the bottom of the tank to a level above the upper level of the heating means whereby the transverse walls define a vapor chamber in each of the compartments above the heating means,

a. each of the transverse walls defining port means whereby the compartments are in communication;

6. a plurality of longitudinal vertical walls extending in each of the compartments from the bottom of the tank into the vapor chamber above the heating means and spaced from each other and from the tank walls to form in each of the compartments two cells laterally adjacent the walls of the tank and at least one central cell,

a. the longitudinal walls defining port means whereby the neighboring cells in each of the compartments are in communication,

b. each cell laterally adjacent the tank walls communicating with the like cell of the upstream or downstream compartment through respective ones of the port means defined in the transverse walls, and

c. the port means in the transverse walls being so arranged that the solution and crystallized solute circulate in a sinuous path through all of the cells from the inlet means to the outlet means of the tank, and

7. the heating means being divided into several sections each positioned in one of the cells and so spaced from at least one of the walls of the cells as to form in each cell a return passage for the solution and crystallized solute under the heating means whereby the solution and crystallized solute rise in each cell through the heating means, vapor from the heated solution amasses in a vapor chamber above the heating means, and the solution and crystallized solute descend through the return passage.

2. The crystallization apparatus of claim I, wherein the heating means is constituted by vertical radiators extending parallel to the longitudinal axis of the tank and passing through a plurality of the compartments, each of the heating means sections consisting of several of said radiators and being spaced laterally from one another.

3. The crystallization apparatus of claim 1, wherein like walls parallel to the longitudinal axis are aligned with each other in asuccession of the compartments.

4. The crystallization apparatus of claim 1, wherein the heating means is divided into two of said sections, said sections being disposed symmetrically in respect of a longitudinal plane of symmetry of the tank, and each section is sub-divided into two sub-sections by a respective ones of the walls parallel to the longitudinal axis.

5. The crystallization apparatus of claim 4, wherein one of the walls parallel to the longitudinal axis is disposed in the plane of symmetry.

6. The crystallization apparatus of claim 1, wherein the heating means is divided into a central one of said sections, the central heating means section being disposed symmetrically in respect of a longitudinal plane of symmetry of the tank, and two lateral ones of said sections, the lateral heating means sections being disposed symmetrically in respect of the plane, and two of the walls parallel to the longitudinal axis are disposed between the central section and the lateral sections of the heating means.

7. The crystallization apparatus of claim 6, wherein one of the walls parallel to the longitudinal axis is disposed in the plane of symmetry. 

2. inlet means for the solution at one end of the tank;
 2. The crystallization apparatus of claim 1, wherein the heating means is constituted by vertical radiators extending parallel to the longitudinal axis of the tank and passing through a plurality of the compartments, each of the heating means sections consisting of several of said radiators and being spaced laterally from one another.
 3. The crystallization apparatus of claim 1, wherein like walls parallel to the longitudinal axis are aligned with each other in asuccession of the compartments.
 3. outlet means for the crystallized solute at an end of the tank opposite to the one end;
 4. heating means positioned in the lower part of the tank;
 4. The crystallization apparatus of claim 1, wherein the heating means is divided into two of said sections, said sections being disposed symmetrically in respect of a longitudinal plane of symmetry of the tank, and each section is sub-divided into two sub-sections by a respective ones of the walls parallel to the longitudinal axis.
 5. The crystallization apparatus of claim 4, wherein one of the walls parallel to the longitudinal axis is disposed in the plane of symmetry.
 5. a plurality of transverse walls separating the tank into a plurality of compartments and extending from the bottom of the tank to a level above the upper level of the heating means whereby the transverse walls define a vapor chamber in each of the compartments above the heating means, a. each of the transverse walls defining port means whereby the compartments are in communication;
 6. a plurality of longitudinal vertical walls extending in each of the compartments from the bottom of the tank into the vapor chamber above the heating means and spaced from each other and from the tank walls to form in each of the compartments two cells laterally adjacent the walls of the tank and at least one central cell, a. the longitudinal walls defining port means whereby the neighboring cells in each of the compartments are in communication, b. each cell laterally adjacent the tank walls communicating with the like cell of the upstream or downstream compartment throuGh respective ones of the port means defined in the transverse walls, and c. the port means in the transverse walls being so arranged that the solution and crystallized solute circulate in a sinuous path through all of the cells from the inlet means to the outlet means of the tank, and
 6. The crystallization apparatus of claim 1, wherein the heating means is divided into a central one of said sections, the central heating means section being disposed symmetrically in respect of a longitudinal plane of symmetry of the tank, and two lateral ones of said sections, the lateral heating means sections being disposed symmetrically in respect of the plane, and two of the walls parallel to the longitudinal axis are disposed between the central section and the lateral sections of the heating means.
 7. The crystallization apparatus of claim 6, wherein one of the walls parallel to the longitudinal axis is disposed in the plane of symmetry.
 7. the heating means being divided into several sections each positioned in one of the cells and so spaced from at least one of the walls of the cells as to form in each cell a return passage for the solution and crystallized solute under the heating means whereby the solution and crystallized solute rise in each cell through the heating means, vapor from the heated solution amasses in a vapor chamber above the heating means, and the solution and crystallized solute descend through the return passage. 